This invention relates to methods for corrugating parts and more particularly to methods for corrugating strut boots having planar end segments joined by an intermediate corrugated segment.
Methods for corrugating hollow parts are known in which an extruder directs a hollow column with respect to moveable die blocks that shape the hollow column end to end with a plurality of convolutions.
Examples of such molded parts and methods are shown in U.S. Pat. Nos. 3,843,758, 4,319,872, 4,439,130, 4,718,844 and 5,531,583. In the past such molded parts have utilized a mold part that involves formation of a plurality of convolutions end to end of the mold block such that the resultant molded part is a corrugated tube suitable for use in irrigation and other like applications.
It is also known to separately mold strut boots and the like that include planar end segments for connection to stationary and moveable members and wherein a plurality of convolutions are formed between the planar end segments for providing for relative movement between the stationary and moveable parts to which the strut boot is attached are formed by one or more molding steps.
While suitable for their intended purpose none of the aforesaid prior art methods are able to meet cost and product rate objectives suitable for meeting the cost requirements of motor vehicle manufacturers and other customers requiring high quality, and low cost parts.
According to the present invention these objectives are met by a method for continuously forming molded parts including providing an extruder, directing a hollow column of plastic material from said extruder; providing a plurality of die blocks each including planar end segments having differing geometry and joined by intermediate convoluted segments; continuously moving such die blocks for receiving and forming the hollow column with planar end segments and intermediate convoluted segments and advancing the shaped column of plastic material from the continuously moving die blocks and providing a cutter synchronized to the movement of the shaped column for separating the planar end segments to form one or more parts having planar end segments of the same or differing geometry in each part or with differing geometry from part to part.
An object of the invention is to provide a process in which such planar end segments are formed with identical geometry and wherein a continuous molded extrusion shape is passed from the moveable mold blocks having a repeating pattern A-B-C-A-B-C defined by the expression (A-B-C)n.
A further object of the invention is to provide a process wherein the end segments are formed with differing geometries and wherein the continuous molded extrusion has a repeating pattern A-B-C-Cxe2x80x2-B-A-A-B-C-Cxe2x80x2-B-A defined by the expression (A-B-C-Cxe2x80x2-B-A)n.
Yet another feature of the invention is to provide extrudent material for the aforesaid process that is a thermoplastic flexible synthetic polymer such as thermoplastic vulcanizates (TPV""s); thermoplastic polyolefins (TPO""s); ionomer resins, such as Surlyn; flexible PVC resins; thermoplastic elastomers (TPE""s); flexible polyurethane polymers and the base is a rigid thermoplastic such as polypropylene; filled polypropylene; talc-filled polypropylene; polyethylene; high density polyethylene; polystyrene; PVC resins; ABS resins; TPO resins; Nylon resins; Metallocene polymers or a flexible thermoplastic material such as thermoplastic vulcanizates (TPV""s); thermoplastic polyolefins (TPO""s); ionomer resins, such as Surlyn; flexible PVC resins; thermoplastic elastomers (TPE""s); flexible polyurethane polymers.